PROJECT SUMMARY/ABSTRACT Tragically, HIV infections among Black men who have sex with men (BMSM) in the U.S. persist. Despite the availability and interest in pre-exposure prophylaxis (PrEP), effective uptake among BMSM remains low. It is imperative to mitigate barriers to PrEP initiation among this group, which could require HIV interventions that incorporate behavioral, biomedical, and structural strategies. The proposed theory-guided, multi-component intervention is designed to enhance HIV risk perceptions and increase PrEP initiation among BMSM in Baltimore City, using an existing mobile smartphone application along with peer change agents to record and review sexual risk behaviors and encourage PrEP initiation. The proposed research and training plan in this Mentored Research Scientist Developmental Award (K01) proposal will provide the principal investigator, Derek T. Dangerfield II, PhD, with the skills needed in intervention design to develop into a productive, independent investigator. The research and training aims proposed address a critical gap in HIV prevention; it is well established that extant work has failed to substantially lower infections among BMSM throughout the U.S. To strategically advance these training aims, this K01 proposal is crafted to facilitate professional development and research capacities as a rising independent investigator. Targeted course work, didactic workshops, and in-depth mentorship from experts in the domains of clinical intervention design, life course theoretical approaches to health, and statistical analysis are incorporated to facilitate hands-on opportunities to apply newly developed skills. The combined use of technology, peers, and PrEP leverages existing relevant prevention strategies for a multi-component intervention. This research is innovative and timely as it responds to federal and academic calls for carefully considerate, interdisciplinary interventions to reduce HIV incidence among priority populations. The aims of this proposal incorporate qualitative and quantitative research methods to explore the preferences of the components of an intervention to increase PrEP initiation among the population. This research has implications for understanding whether the methods used in this intervention can be applied in clinical settings or can be applied in peer-based settings to circumvent the barriers of traditional healthcare engagement. Dr. Dangerfield will be primarily mentored by senior investigator Jason Farley, PhD, MPH, ANP-BC, FAAN at the Johns Hopkins School of Nursing, with additional mentoring from Drs. Chris Beyrer (Johns Hopkins Bloomberg School of Public Health), Ricky Bluthenthal (University of Southern California Keck School of Medicine), and Renata Arrington-Sanders (Johns Hopkins School of Medicine). Through research and didactic mentoring and training, Dr. Dangerfield will build upon his expertise in behavioral social science to develop a successful career in designing high-impact, multicomponent clinical interventions and reduce health disparities.